Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Localization of chitin synthetase in cell-free homogenates of Saccharomyces cerevisiae: chitosomes and plasma membrane

Abstract: We describe an improved method for fractionating cell-free extracts of Saccharomyces cerevisiae to separate its membranous components by a combination of isopycnic and velocity sedimentations. These procedures were used to examine the subcellular distribution of chitin synthetase (chitin-UDP acetylglucosaminyltransferase; EC 2.4.1.16) in homogenates from exponentially growing walled cells of a wild-type strain of yeast. Chitin synthetase (Chs1) activity was mainly found in two distinct vesicle populations of nearly equal abundance but with markedly different buoyant densities and particle diameters. One population contained 45-65% of the total chitin synthetase and was identified as chitosomes because of microvesicular size (median diameter = 61 nm) and characteristic low buoyant density (1.15 g/ml); it also lacked 1,3-beta-glucan synthetase activity. The second population (35-55%) was identified as plasma membrane because of its high buoyant density (1.22 g/ml), large vesicle size (median diameter = 252 nm), and presence of vanadate-sensitive ATPase. This fraction cosedimented with the main peak of 1,3-beta-glucan synthetase. A third, minor population of chitin synthetase particles was also detected. Essentially all of the chitin synthetase in the two vesicle populations was zymogenic; therefore, we regard these vesicles as precursors of the final active form of chitin synthetase whose location in the cell has yet to be unequivocally determined.

The crystal structure of chitin and chitosan

Abstract: Roentgenographic studies are performed to investigate the structural changes in chitin under pressure and shear during its solid-state processing using a twin-screw extruder and Bridgman anvils. The structure of chitosan synthesized by the solid-phase method is studied. Deformation under the conditions of dry extrusion grinding at room temperature reduces the crystallinity of the original chitin. Addition of water restores the crystallinity of the material up to the value characteristic of the original chitin. Extrusion processing of chitin at room temperature with addition of water virtually preserves the crystallinity and degree of ordering of the chitin crystal lattice, the same as ordinary dry grinding at an elevated (180°C) temperature. The maximum degree of amorphization of chitin is attained by its processing on Bridgman anvils. Solid-state synthesis of chitosan from chitin leads to a product with a more amorphous structure in comparison with chitosan produced by the suspension method.

Chitin and chitosan stimulate canine polymorphonuclear cells to release leukotriene B4 and prostaglandin E2

Abstract: The effects of chitin and chitosan on the release of arachidonic acid products were investigated in this study. Supernatants of canine polymorphonuclear cell (PMN) suspensions incubated with chitin and chitosan contained a leukotriene B4 (LTB4) concentration high enough to induce canine PMN migration in vitro. The supernatants also contained the same concentration of prostaglandin E2 (PGE2) as that normally found in the peripheral blood of dogs. Intraperitoneal administration of chitosan to dogs induced peritoneal exudative fluid (PEF), but chitin did not. The PEF contained numerous PMNs and macrophages. The supernatant of PEF contained both heat-stable and heat-labile chemotactic factors for canine PMNs. It also contained enough LTB4 to attract the canine PMNs in vitro.